In general, a torque converter is installed between an engine and a transmission of a vehicle and serves to transmit driving power of the engine to the transmission by using a fluid. If a load applied to the engine is increased, power transmission efficiency of the torque converter may deteriorate, and therefore, the torque converter has a lock-up clutch (also called a ‘damper clutch’) which is a means for directly connecting the engine and the transmission. The lock-up clutch is disposed between the turbine and a front cover directly connected to the engine and enables rotational power of the engine to be transmitted directly to the transmission through the turbine.
The lock-up clutch includes a piston that may be moved in an axial direction of a turbine shaft. Further, a core plate is disposed between the piston and the front cover, and friction members are coupled to both sides of the core plate. Further, a damper for a torque converter, which may absorb impact and vibration applied in a rotation direction of the shaft, is coupled to the core plate.
In a damper system for a torque converter, springs are generally disposed in parallel, such that the springs absorb the same load.
However, in the damper system for a torque converter, rigidity of a damper spring needs to be decreased to reduce gear shift impact, and to this end, a configuration in which the springs are connected in series has been proposed. A serially-connected damper system in the related art has a configuration in which multiple springs are connected in series on the same circumference. In the torque converter having the serially-connected damper system, there are problems in that an operating radius of a spring or a damper system is restricted due to a limitation on durability and mounting spaces of the springs, and implementation of low rigidity and a wide angle is restricted.